1. Field of the Invention
The present invention relates to an optical fiber amplifying module which amplifies input light with an amplification optical fiber.
2. Related Background Art
Optical fiber laser light sources have been known as highly-reliable, small-size light sources, and their beam quality is favorable in particular since they have a waveguide structure. Therefore, the optical fiber laser light sources have been widespread in various uses such as processing in electronic/mechanical fields, medicine, measurement, and optical communications.
In particular, optical fiber laser light sources of MOPA (Master Oscillation Power Amplifier) structure in which pulsed seed light outputted from a seed light source is amplified by an optical fiber amplifying module show no pulse width expansion under the influence of the delay in propagation due to the fiber length and the like as compared with currently prevailing light sources of Q-switch structure. Namely, the above-mentioned optical fiber amplifying modules are advantageous in shortening pulses and raising repetition frequencies, and thus are expected to become common in uses of fine processing and measurement. When employed in uses requiring high output such as processing by utilizing a semiconductor laser light source which can be modulated at high speed, it is necessary for optical fiber amplifying modules to have a high gain of 50 dB or more. The high gain is easy to attain in principle, since an amplifying action in the optical fiber amplifying module is usually realized by an amplification optical fiber doped with a rare-earth element or the like.